Only Eagle� is a complete system-engineered drivetrain designed tested and proven to deliver the lightest highest-performing most durable system for all riders on any trail. Eagle� technology provides an expanded optimum gear range making you fast on the flats giving you control on the climbs and unleashing your speed on the descents. Featuring SRAM�s X-SYNC�2 tooth profile chainring the GX crankset is engineered for complete chain control. Compatible with all levels of Eagle drivetrain systems. Optimized 7000 series forged aluminum arms. Fat 4` model is compatible with GXP 100mm/PF GXP 121mm bottom brackets